Normally, when an internal combustion engine having a valve timing controlling apparatus is operated, the cam shaft receives resistance from a valve spring. Therefore, the relative phase of the first rotary body rotatable together with the cam shaft tends to be lagged, relative to the rotation of the second rotary body rotatable together with the crank shaft. In order to solve such phase lag, the conventional valve timing controlling apparatus includes a torsion coil spring for urging the first rotary body to the advancing side relative to the second rotary body.
Another purpose of providing such torsion coil spring relates to startup of the internal combustion engine. The startup is often effected with hydraulically locking the first rotary body and the second rotary body under a predetermined phase condition. However, at the time of startup, the oil supply is insufficient for effecting the phase control, so that the locking can be difficult because the first rotary body tends to move back and forth relative to the second rotary body. In particular, when the first rotary body is located on the lagging side, the resistance applied to the cam shaft resists advancing of the first rotary body, so that the locking cannot be done speedily. For this reason, the torsion coil spring is provided for enabling the apparatus to effect the locking operation speedily.
An example of the valve timing controlling apparatus of the above-noted type is known from Patent Document 1 identified blow, shown as Prior-Art Document Information relating to the present invention. In the case of the valve timing controlling apparatus disclosed in this Patent Document 1, there is provided a gap between a coil spring portion of the torsion coil spring and the respective peripheral face of the first rotary body or the second rotary body. With this, even when the coil spring portion is reduced in its inner diameter during relative rotation between the first rotary body and the second rotary body, it is possible to avoid the trouble that excessive frictional resistance generated due to contact between the coil spring portion of the torsion coil spring and the respective peripheral face prevents the torsion coil spring from exerting its initial set spring force.
Patent Document 1: Japanese Patent Application “Kokai” No. 2002-276312 (paragraphs: 0014, 0032, and FIG. 1).